Abstract

Dopamine is a neurotransmitter (or chemical messenger) found in diverse organisms ranging from simple invertebrates to humans.
It is also a required intermediate in the formation of the neurotransmitters noradrenaline and adrenaline. Although found
in a number of vertebrate tissues, dopamine's most important effects are due to robust expression in a relatively small number
of central nervous system neurones that have widespread projections. Dopamine signalling affects a correspondingly wide variety
of physiological functions, from gastrointestinal motility and pituitary hormone release, to voluntary movements, motivation
and reward, and higher cognitive processes. Although dopamine neurotransmission is normally a highly regulated process, drugs
have been developed to modify its signalling. Some commonly used drugs affect dopamine neurotransmission indirectly (by changing
its synthesis, release, reuptake or inactivation), whereas other drugs more directly mimic or block the actions of dopamine
at its biological targets (i.e. multiple cell surface dopamine‐responsive receptors). An astonishingly broad range of central
nervous system disorders (including Parkinson disease, schizophrenia, attention deficit hyperactivity disorder, and sleep
disorders), and other medical conditions (such as nausea, excessive pituitary hormones, gastrointestinal disorders, and cardiovascular
shock) are currently treated using such drugs.

Key Concepts:

Dopamine is a neurotransmitter in the brain and elsewhere, as well as an intermediate in the biosynthesis of the neurotransmitters
noradrenaline and adrenaline.

Dopamine synthesis is regulated by a rate‐limiting enzyme, and its extracellular concentrations controlled by an active recapture
mechanism and several metabolic enzymes.

The effects of dopamine are mediated by a family of G protein coupled receptors linked to distinct intracellular signalling
pathways.

Though relatively few in number, dopamine‐containing neurons originating in the mammalian midbrain send branching fibres that
innervate widespread areas of the forebrain.